Simple, easily integrated voltage comparators are known. U.S. Pat. No. 4,812,681 discloses a comparator formed of two cascade connected inverters of NMOS type. U.S. Pat. Nos. 5,237,326 and 5,451,952 respectively disclose two different comparators based on respective inverters of CMOS type, and two analog-to-digital converters of the flash type employing multiple comparators.
With all of the above comparators, an accurate setting of the threshold voltage is not readily achieved, since the threshold voltage is dependent on an external reference voltage and/or on the W/L ratii.